It has long been a problem of harvesting equipment to determine the amount of grain which has been stored within the bin of the combine. Initially, it was necessary for the operator to turn around and physically look into the grain bin to see the level of grain. As the cost of crop production rises, any spillage of grain becomes more and more expensive for the farmer, and it therefore becomes critical to ensure that the grain bin does not overflow onto the ground. Many combines now utilize grain bin extensions, making the bin taller than the top of the cab, and thereby preventing viewing from within the cab.
Various monitoring systems are now available for harvesters which are much more effective than requiring the operator to physically view the contents of the combine grain bin. A majority of the most common monitoring systems utilize a mechanical switch or float within the grain bin which will trigger a light in the cab when the grain has reached the "full" line. While conventional monitors were a great advance over physical viewing of the bin contents, they still suffer several drawbacks.
First, many farms today utilize sloped or hilly grounds for crop production. Because conventional grain monitor switches are located centrally within the bin, it is possible for grain to overflow over the side edge of the grain bin on a side hill before the level of grain within the center of the bin activates the mechanical switch to indicate "full".
Another problem with current bin monitoring systems is in the fact that a signal lamp is only activated once the grain has completely filled the bin. If the operator desires to continue harvesting while the grain bin is unloaded into a wagon traveling beside the harvester, it typically causes a delay for the combine operator to report the "full" condition to the grain hauler located at the side of the field. Thus, much of the time saved in continued harvesting is lost during the wait for the grain hauler to bring the empty wagon alongside the combine.
Finally, most current grain monitoring systems utilize mechanical devices having moving parts. The more moving parts present within the grain bin, the greater the likelihood of repair or replacement of the monitoring system.